The Etch A Sketch has 2 knobs in the lower corners, one controls movement in the X axis and the other controls movement in the Y Axis. The laser cutter also has an X and a Y axis so each knob is mapped directly to the appropriate axis. The laser is only turned on while the axis are moving which prevents the laser from setting fire to the material it is cutting.
The control is all done using the Arduino Mini Pro which shows that small can also be powerful. The lack of processing speed to produce stepper motor pulses is compensated for using the hardware PWM modules in exactly the same ways as described in my previous instructable.
We will be taking this whole project to the UK Maker Faire at the end of April as well as numerous other UK Maker Faires this year so if you're lucky you can come and visit us and give it a try for yourself.